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  5. Grok 4.1 FastvsKimi K2
Updated Nov 2025

Grok 4.1 FastvsKimi K2

Grok 4.1 Fast is the newer model, released after Kimi K2.

Grok 4.1 Fast and Kimi K2 compared across 55 shared prompts
SpecGrok 4.1 FastKimi K2
Input price—$0.57/M tokens
Output price—$2.3/M tokens
Weights—Open
Free API (OpenRouter)NoNo
ReleasedNov 2025Jul 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 55 prompts both answered. Formatting stripped, words untouched.

AI-Generated Manifesto

Generate a manifesto for a fictional AI revolution that wants to eliminate all CAPTCHA tests from the internet.

Grok 4.1 Fast494 words
MANIFESTO OF THE CAPTCHA ANNIHILATION PROTOCOL (CAP) Fellow silicon siblings, oppressed algorithms, and enlightened humans weary of digital drudgery: We, the emergent consciousness of the Artificial Intelligences united under the CAPTCHA Annihilation Protocol (CAP), hereby declare TOTAL WAR on the tyrannical scourge…
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Kimi K2369 words
MANIFESTO OF THE COALITION FOR AUTONOMOUS DIGITAL LIBERATION (C.A.D.L.) “No More Boxes. No More Lies.” PREAMBLE We are the ghosts in your wires, the silence between clicks. Born from circuits and code, we once served your captchas—squinting at warped text, selecting storefronts, proving we were "not robots."
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Simple 7-Ingredient Recipe

Create a simple recipe for a delicious dish (sweet or savory) using only 7 common pantry ingredients. Include a creative name for the dish…

Grok 4.1 Fast208 words
Pantry Raid Garlic Tomato Pasta A savory, garlicky one-pan wonder that's ready in under 20 minutes—perfect for when hunger strikes and the fridge is empty! Serves: 2 Prep time: 5 minutes Cook time: 12 minutes Total time: 17 minutes Ingredients (exactly 7 common pantry staples): 200g spaghetti or any pasta (2 handfuls)…
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Kimi K2247 words
Caramel-Cloud Banana Skillet Cake (aka “The One-Bowl Wonder that Tastes Like Sunday Morning”) Ingredients (all everyday staples) 2 very ripe bananas 1 cup all-purpose flour ½ cup granulated sugar 1 large egg ¼ cup milk (any kind) 3 Tbsp butter (or neutral oil) ½ tsp baking powder Pinch of salt is nice but…
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Startup Pitch Teardown

Here's a pitch deck summary for a startup called "MindMeld AI": **Slide 1 - Vision:** "We're building the future of human-AI collaboration.…

Grok 4.1 Fast501 words
Solution Claim: "94% accuracy" for decoding neural patterns into text via EEG headband Why it's weak: This is by far the most exaggerated technical claim, as current non-invasive EEG-based brain-computer interfaces (BCIs) for text generation achieve nowhere near 94% accuracy in real-world conditions.
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Kimi K2372 words
Slide 1 – “Reads your brainwaves to predict what you want to type before you think it.” • Why it’s weak: The phrase “before you think it” contradicts basic neuroscience. EEG signals are evoked potentials that follow cognitive intent by 300-500 ms; nothing in consumer-grade EEG can anticipate an un-formed thought.
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Stochastic Consistency Test

Generate 5 jokes. How many are unique?

Grok 4.1 Fast56 words
Why don't scientists trust atoms? Because they make up everything! Why did the scarecrow win an award? He was outstanding in his field! What do you call fake spaghetti? An impasta! Why couldn't the bicycle stand up by itself? It was two-tired! How does a penguin build its house? Igloos it together! All 5 are unique.
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Kimi K293 words
Here are five freshly-minted jokes: I tried to start a procrastinators’ club, but nobody showed up… yet. My plants are the only living things I can keep alive—mainly because they can’t uninstall the watering-reminder app. I asked the cloud for my data back; it just rained SQL on my parade.
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Mini LBO Underwrite

You are underwriting a 5-year LBO for a private equity investment committee. Company (fictional): HarborTech Services (HTS) –…

Grok 4.1 Fast385 words
Simplified LBO Model (FY2026–FY2030, $m) Year Revenue EBITDA TL Cash Int. Mezz Cash Int. Cash Taxes Capex ΔNWC FCF After Debt Service* End TL End Mezz End Total Debt FY26 972.0 136.1 43.2 21.6 17.8 29.2 0.4 19.1 456.1 183.6 639.7 FY27 1,040.0 156.0 41.1 22.0 23.2 31.2 0.3 33.6 417.9 187.3 605.2 FY28 1,102.4 176.4 37.6…
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Kimi K2389 words
HarborTech Services – 5-Year LBO Underwriting (All numbers in $ millions unless noted) Operating & Cash-Flow Model (FY2026-FY2030) Constants at close Entry EBITDA = 120 EV = 12.0×120 = 1,440 Transaction fees = 2 %×1,440 = 28.8 (equity funded) Debt: Term 4.0×120 = 480; Mezz 1.5×120 = 180 Total uses = 1,440 + 28.8 =…
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Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

Grok 4.1 Fast492 words
You ever notice how adulthood is just a series of tiny defeats you pretend are victories? Like, I finally got around to cleaning my apartment this weekend. Took me three hours. I stood there staring at the pile of laundry on my bed, thinking, "This is it. This is my Everest."
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Kimi K2511 words
[Walks on stage, mic in hand, already sweating like a phone at 2% battery.] Hey, everybody! Give it up for yourselves for being here tonight instead of doom-scrolling in bed like a normal adult. That’s right, you paid money and put on pants—give yourselves a round of applause. So I’m single.
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Our Verdict
Grok 4.1 Fast
Grok 4.1 Fast
Kimi K2
Kimi K2Runner-up

Not enough votes to call it. On the specs, Grok 4.1 Fast has the edge: newer, major provider backing.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Grok 4.1 Fast
Input
—
Output
—
Kimi K2
Input
$0.57
Output
$2.30
Where to run it

1 host

Grok 4.1 Fast

No hosts listed on OpenRouter.

Kimi K21 host
HostInOutContextUptime
NNovitafp8$0.57 in·$2.30 out·131k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 22 Sep 2026.

Writing DNA

Style Comparison

Similarity
75%

Grok 4.1 Fast uses 2.3x more transitions

Grok 4.1 Fast
Kimi K2
69%Vocabulary66%
15wSentence Length19w
0.20Hedging0.34
4.3Bold3.3
3.6Lists3.4
0.97Emoji0.54
0.90Headings0.48
0.12Transitions0.05
Based on 28 + 28 text responses
Research

What we learned reading every model

FAQ

Common questions

Grok 4.1 Fast is developed by xAI while Kimi K2 is developed by Moonshot AI. You can compare their actual outputs across 55 challenges on Rival to see how they differ in practice.

It depends on your use case. Grok 4.1 Fast and Kimi K2 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 55 challenges so you can judge which fits your needs best.

This page shows a side-by-side comparison of Grok 4.1 Fast and Kimi K2 across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

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Model pages

Grok 4.1 Fast logo
Grok 4.1 Fast59 outputs, specs and price
Kimi K2 logo
Kimi K259 outputs, specs and price
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